Test 12F - Bus Bias Level Or Bus (+/-) Open (Exc Wrangler)

WARNING: This page is about a different car, the 1995 Jeep Wrangler, 1995 Jeep Grand Cherokee, and 1995 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION in this article. For appropriate wiring diagram, see WIRING DIAGRAMS section at the end of this article.

CAUTION: Always turn ignition switch to OFF position prior to disconnecting or connecting any module connector.

This test covers following BUS BIAS LEVEL OR BUS (+/-) OPEN trouble codes. Ignition off during BUS test is the most common cause for these messages.

BUS BIAS LEVEL TOO LOW
BUS BIAS LEVEL TOO HIGH
BUS (+) OPEN
BUS (-) OPEN
BUS (+) & BUS (-) OPEN
1. If ignition was off, turn ignition on (engine off). If ignition was on, disconnect Automatic Temperature Control (ATC) module connector, if equipped. Disconnect scan tool from Data Link Connector (DLC). Using an external voltmeter, check voltage between Data Link Connector (DLC), CCD BUS positive circuit (Violet/Brown wire) and ground. If voltage is not 2.3-2.6 volts, go to step 3).
2. If voltage is 2.3-2.6 volts, check voltage between DLC, CCD BUS negative circuit (White/Black wire on XJ body; White/Gray wire on ZJ body) and ground. If voltage is not 2.3-2.6 volts, go to next step. If voltage is 2.3-2.6 volts, replace scan tool cable or cartridge as necessary. Perform TEST VER-1 .
3. Turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Using an external ohmmeter, check resistance between PCM pins No. 26 and 46. If resistance is not 100-140 ohms, replace PCM. Perform TEST VER-1 .
4. If resistance is 100-140 ohms, check resistance of CCD BUS positive circuit (Violet/Brown wire) between PCM connector terminal No. 26 and DLC. If resistance is more than 5 ohms, repair open Violet/Brown wire. Perform TEST VER-1 .
5. If resistance is less than 5 ohms, check resistance of CCD BUS negative circuit (White/Black wire on XJ body; White/Gray wire on ZJ body) between PCM connector terminal No. 46 and DLC. If resistance is more than 5 ohms, repair open CCD BUS negative wire. Perform TEST VER-1 .
6. If resistance is less than 5 ohms, disconnect Vehicle Theft Security System (VTSS) module connector, if equipped. If vehicle is not equipped with VTSS, go to step 12). Using an external ohmmeter, check resistance between VTSS module pins No. 1 and 2. See Figure. If resistance is not 100-140 ohms, replace VTSS module. Perform TEST VER-1 .
7. If resistance is 100-140 ohms, check resistance of CCD BUS positive circuit (Violet/Brown wire) between VTSS module connector terminal No. 2 and DLC. If resistance is more than 5 ohms, repair open Violet/Brown wire. Perform TEST VER-1 .
8. If resistance is less than 5 ohms, check resistance of CCD BUS negative circuit (White/Black wire on XJ body; White/Gray wire on ZJ body) between VTSS module connector terminal No. 1 and DLC. If resistance is more than 5 ohms, repair open CCD BUS negative wire. Perform TEST VER-1 .
9. If resistance is less than 5 ohms, reconnect scan tool. Using scan tool in voltmeter mode, check voltage on VTSS module connector terminal No. 3, fused ignition switch output circuit (Dark Blue/White wire on XJ body; White/Black wire on ZJ body). If voltage is less than 10 volts, repair open fused ignition switch output circuit. Perform TEST VER-1 .
10. If voltage is more than 10 volts, turn ignition off. Using scan tool in ohmmeter mode, check resistance of VTSS module connector terminals No. 11 or 19, system ground circuit (Black wire).
11. If resistance is more than 5 ohms, repair open to ground in Black wire. Perform TEST VER-1 . If resistance is less than 5 ohms, replace VTSS module. Perform TEST VER-1 .
12. Turn ignition off. Disconnect Controller Anti-Lock Brake (CAB) module connector. Check resistance between CAB pins No. 23 and 42. If resistance is not 100-140 ohms, replace CAB. Perform TEST VER-1 .
13. If resistance is 100-140 ohms, check resistance of CCD BUS positive circuit (Violet/Brown wire) between CAB connector terminal No. 23 and DLC. If resistance is more than 5 ohms, repair open Violet/Brown wire. Perform TEST VER-1 .
14. If resistance is less than 5 ohms, check resistance of CCD BUS negative circuit (White/Black wire on XJ body; White/Gray wire on ZJ body) between CAB connector terminal No. 42 and DLC. If resistance is more than 5 ohms, repair open CCD BUS negative wire. Perform TEST VER-1 .
15. If resistance is less than 5 ohms, reconnect scan tool. Using scan tool in voltmeter mode, check voltage on CAB connector terminal No. 53, fused ignition switch output circuit (Light Green/Yellow wire on XJ body; Light Green/Dark Green wire on ZJ body). If voltage is less than 10 volts, repair open fused ignition switch output wire. Perform TEST VER-1 .
16. If voltage is more than 10 volts, turn ignition off. Using scan tool in ohmmeter mode, check resistance of CAB connector terminal No. 1, ground circuit (Black wire). If resistance is more than 5 ohms, repair open to ground in Black wire. Perform TEST VER-1 . If resistance is less than 5 ohms, replace scan tool cable or cartridge as necessary. Perform TEST VER-1 .

NOTE: Test procedures skip from TEST 12F to TEST 12J. No test procedures have been omitted.